(1) Field of the Invention
The present invention relates to laminated materials of the type suitable for use as panels, e.g. as interior door panels of cars or other vehicles, or as furniture elements and similar uses.
(2) Description of the Prior Art
Generally, such panels have a structural as well as a decorative function and are made as disclosed e.g. in U.S. Pat. Nos. 4,243,456, 4,328,067 and in GB No. 2,195,940 by press-molding a substrate layer or sheet of a normally rigid, i.e. non-pliable, thermoplastic material having a typical thickness between about 1 and 10 mm and a cover layer sheet of a normally pliable decorative material. Examples of suitable materials for both the thermoplastic substrates, e.g. polypropylene/wood particle composites, as well as for the cover material layers, e.g. polymer sheeting and textile materials, are given in the patents mentioned above. The sheet of the thermoplastic substrate material that is introduced into the laminating and molding press in a heat-plastified state is shaped while, simultaneously, the sheet of the cover layer material is bonded to the substrate that is being formed in the press. Thus, molding and lamination is effected in a one-step process and the bonding action is frequently but not necessarily due to the adhesive effect of a thermoplastic constituent of the substrate when in a heat-plastified state.
Two specific problems have to be resolved when operating such methods: one is "edge-covering", i.e. coating or camouflaging of the panel edge, for instance by an overlapping edge portion of the decorative cover layer that is folded around the edge and affixed to the backside of the panel.
The other problem arises when the decorative cover layer has two or more segments of differing color and/or texture, such as when a polymer sheeting of a given color, shade or hue should cover one part of the panel while a textile layer having the same or a differing color, shade or hue and a differing texture, e.g. the feel and appearance of velvet or cloth, should cover another part of the panel, and when the differing segments are to cover rather well-defined specific portions of the panel surface as determined by aesthetic necessity or/and product design.
For the purpose of the invention, a cover layer having two or more segments of differing visual and/or tactile appearance will be termed a "differentially segmented cover layer" or "segmented cover" for brevity; in analogy, the sheet material used for producing such a cover layer will be termed "differentially segmented sheet" or "segmented sheet". Adjacent segments of the segmented sheet will be connected by a "seam" that may have the form of a straight or curved line, or it may be a branched or looped line or have any other configuration depending upon number, shape and position of the segments that form the sheet and the term "seam line" as used herein is intended to include seam configurations independently of shape and without regard to the method used for forming the seam, e.g. by physical means including adhesion with or without adhesives, sewing, welding, or chemical means including interfusion cross-linking, etc.
Generally, the actual seam line(s) of the segmented sheet should be brought "into register" or made to "coincide" with a predetermined or theoretical seam line position on the panel, e.g. along a certain line in a plane, or along a certain contour of a spatial shape; an illustrative example is an armrest of a door panel where, for example, the horizontal armrest portion is to consist of velvet for comfort while the vertical side of the armrest, or a lower panel portion, is to consist of en embossed plastics material, e.g. for high wear resistance. Consequently, the problem is how to get the seam line, or lines, of the sheet used to form the cover layer to coincide with its predetermined or theoretical position on the final laminated panel.
One general prior art method of getting the seam line of a segmented cover sheet into a predetermined position on the "frontside" (i.e. the panel side intended for visual and/or tactile exposure) consists of pre-connecting the seam line portion of the cover sheet with the substrate layer before actually connecting the main portion of the cover sheet and the substrate, with or without simultaneously shaping the resulting panel. Such a method will be termed a "seam fixing method" hereinafter and a prior art example of such a method using clamp means for seam fixing is disclosed in DE No. 31 09 338.
However, seam fixing will have an advantageous effect only if--before actual fixing--the seam line of the segmented sheet for forming the cover layer is brought into register with its theoretical position on the molded or mold-supported substrate. Considering the realities of mass-producing such items as interior panels for use in furniture or cars, trucks, busses, ships, planes, etc., it will easily be understood that off-register positions, also termed "off-set" positions, of the seam line before seam fixing cannot always be prevented and will lead to production losses or low quality products.